Signature validation bypass in ServiceStack
ServiceStack before 5.9.2 mishandles JWT signature verification unless an application has a custom ValidateToken function that establishes a valid minimum length for a signature.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| .NET (NuGet) | ServiceStack | < 5.9.2 | 5.9.2 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2020-28042
- https://github.com/ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee
- https://forums.servicestack.net/t/servicestack-v5-9-2-released/8850
- https://snyk.io/vuln/SNYK-DOTNET-SERVICESTACK-1035519
- https://www.nuget.org/packages/ServiceStack
- https://www.shielder.it/advisories/servicestack-jwt-signature-verification-bypass
- https://www.shielder.it/blog/2020/11/re-discovering-a-jwt-authentication-bypass-in-servicestack
- Weakness (CWE)
CWE-347- Platform
- .NET (NuGet)
- Package
ServiceStack- Disclosed
- 13.01.2021
- Updated
- 11.10.2026 11:23
Sources and licenses
OSV / GitHub Advisory Database - GHSA-v5rv-hpxg-8x49 - CC BY 4.0
Vulnerability history: ServiceStack
All published vulnerabilities of this package (.NET (NuGet)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 01.2021 05.2022
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Medium 2
Disclosures per year
- 2021: 1
- 2022: 1
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 0
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